在以下情况下如何访问json数据并在if条件下使用？

Question

Following is my AJAX function code:

$('#request_form').submit(function(e) {
    var form = $(this);
    var formdata = false;

    if (window.FormData) {
        formdata = new FormData(form[0]);
    }

    var formAction = form.attr('action');

    $.ajax({
        url         : 'xyz.php',
        type        : 'POST',    
        cache       : false,
        data        : formdata ? formdata : form.serialize(),
        contentType : false,
        processData : false,
        success: function(response) { 
            //Here I'm facing issue in checking whether the $response[error_message] is empty or not
            if (!response.error_message)
                alert(response.error_message); 
        }
    });
    e.preventDefault();
});

Here in response following is the content coming from PHP. This content is already converted into json format using the method json_encode()

{
    "error_message": "Id can't be blank<br>Please select Date<br>Image can't be blank<br>"
}

I want to check whether the array response[error_message] and if it's not empty then I want to show the content in alert box otherwise do nothing.

Please help me in this regard.

thanks in advance.

Answer 1

Try this:

<script>
$('#request_form').submit(function(e) {
    //This should be the first line
    e.preventDefault();

    var form = $(this);
    var formdata = false;

    if (window.FormData) {
        formdata = new FormData(form[0]);
    }

    var formAction = form.attr('action');

    $.ajax({
        url         : 'xyz.php',
        type        : 'POST',    
        cache       : false,
        data        : formdata ? formdata : form.serialize(),
        contentType : false,
        processData : false,
        success: function(response) { 

            var responseObject = $.parseJSON(response);

            //Here I'm facing issue in checking whether the $response[error_message] is empty or not
            if (responseObject.length != undefined && responseObject.length > 0)
                alert(responseObject.error_message); 
        }
    });

}); 
</script>   

Answer 2

Use :

if ( response.hasOwnProperty('error_message') &&  '' != response.error_message ){
  alert(response.error_message) ;
}